1. Field of the Invention
This invention relates to an improvement in a camera device, and more particularly to a film winding device capable of carrying out film winding and rewinding operations stably, lightly and soothly, minimizing the power consumption of an automated device of this kind using a motor, miniaturizing such an automated film winding device with ease, employing without trouble an auto-loading system and an automatic rewinding system, in which no preparatory operations for the rewinding of a film are required, and leaving an end of a cartridge-contained film not wound into the cartridge during the rewinding thereof.
2. Description of the Prior Art
There are the following two types of known film winding devices for cameras, which employ a winding spool and a sprocket.
The first type of film winding device employs a sprocket-driving system, in which a film to be wound is fed by a sprocket by a predetermined amount (corresponding to one frame) each time to be taken up around a winding spool as the sprocket and spool are rotated simultaneously. The second type of film winding device employs a sprocket-driven system, in which a film to be wound is fed by a winding spool alone with a sprocket used solely for controlling a take-up amount of the film. In the first type of film winding device, a friction clutch is provided between a winding shaft and the winding spool so as to compensate the difference between the film feed speed of the sprocket and the film take-up speed of the winding spool, which occurs when the diameter of the winding of film on the winding spool is varied. When such a friction clutch is used, not only the winding resistance is increased but also a film winding operation becomes unstable. Especially, when a motor is used to wind a film, an increase in the winding resistance results in an increase in the power consumption thereof, and it naturally becomes necessary that the power and size of the motor be increased. This hinders the miniaturization of a camera. In addition, an unstable film winding operation referred to above has an adverse effect on a camera device employing a film autoloading system. On the other hand, in the second type of film winding device, a friction clutch is not used but a film is wound as it is drawn by the wind spool. Accordingly, a film winding angle is varied in accordance with a change in the diameter of the winding of film on the winding spool. As the diameter of the winding of film is increased, a winding resistance is also increased. Moreover, since a film to be loaded is not fed by the rotation of the sprocket, it is difficult to employ an auto-loading system. This constitutes a great disadvantage of this type film winding device.
The above two types of film winding devices will be discussed with respect to the film rewinding operations thereof. In the first film winding device employing a sprocket-driving system, it is necessary that a preparatory operation for setting the sprocket in a freely rotatable state by carried out before rewinding the film. In the second film winding device employing a sprocket-driven system having, for example, a winding lever, it is necessary that a preparatory operation for cutting the connection between the winding shaft and winding spool by a certain means be carried out before rewinding the film. The latter preparatory operation also requires to be carried out in the first film winding device. In order to carry out the rewinding of a film without conducting such a preparatory operation, it is necessary that a friction clutch be provided between the winding shaft and winding spool to slide the latter. However, when a friction clutch is provided to slide the winding spool, a rewinding load is increased greatly, so that the power consumption of the film rewinding device, which is driven by a motor, is much increased. This makes it necessary to increase the power and size of the motor, and hinders the miniaturization of a camera.
In any of the above two types of film winding devices, in which a cartridge-contained film is used, a winding load is increased to a great extent as an amount of the film, which is being wound, and which remains in the cartridge, is decreased. It is considered that the causes of this problem reside in the following. The spool is held in the cartridge in a simple form having a comparatively high bearing resistance. As the diameter of the winding of film on the spool is decreased, a tensile force of the film for rotating the spool is increased, and an angle of bend of that portion of the film which is at an outlet of the cartridge becomes acute, so that a film-drawing resistance is increased. When an amount of the film remaining in the cartridge is large, the diameter of the winding of film is large. In such a case, a large rotary torque is applied to the spool, and the film is drawn out without being bent greatly at the outlet of the cartridge, even if a tensile force of the film is low. Thus, the film is wound with a low resistance. When an amount of the film remaining on the spool has become small, i.e. after around 30 frames of a cartridge-contained 36-frame roll film have been paid out, a high tensile force of the film is required for rotating the spool, and, moreover, an angle of bend of that portion of the film which is at the outlet of the cartridge becomes acute. Accordingly, the spool is pressed at the flange thereof strongly against a light-shielding member provided in the vicinity of the outlet of the cartridge. Thus, a winding load is increased as mentioned above, and the power consumption of the film winding device, which is driven by a motor, is increased greatly. This makes it necessary to increase the power and size of the motor, and hinders the miniaturization of a camera device.